Sorry if this question has been asked already. I am reading this paper on the kinematic analysis of a delta robot here: robotics.caltech.edu/~jwb/.../DescriptiveGeometryDeltaRobot.pdf
I encountered something called the moment of the normal direction vector. It is mentioned in page 4 of the paper, under the homogeneous coordinates of the thigh planes. My question is, what is this moment of normal direction vector?
Also in the paragraph above the equations of thigh planes (the very first paragraph of page 4) the author mentioned two solutions for E obtained by intersections of two planes. I think the two planes are normal to each other (plane of the thigh circle and the plane of (the intersection of the sphere centered on D and the circle centered on C)). I wish I could provide a separate picture. Is my understanding correct? Sorry if I didn't make any sense.
Thank you for your patience. I really appreciate your help.